This invention relates to a method of producing a compact of amorphous alloy by using powders of amorphous alloy, which compact is advantageously applicable to various kind of magnetic materials.
Regarding a conventional warm extrusion compacting method there is, for example, an invention disclosed in the U.S. Pat. No. 4,377,622. According to this prior art method, filament of amorphous alloy is filled in a metal container in a density of 50 to 60% of the theoretical density thereof, then the container being sealed by a plug so as to be used as a billet to be subjected to extrusion, next the thus prepared billet being heated to a substantially uniform working temperature between plasticity transition temperature and crystallization temperature of the alloy, subsequently the billet being subjected to warm extrusion working with a reduction of area of at least 3.5 to 1 (about 70%) to obtain a columnar compact of amorphous alloy. Disclosed further as another example is a method in which a core member is placed concentrically in a central part of a container and the filament of amorphous alloy is filled in a space defined between the core member and the inner wall of the container, then the container together with the filaments, after it has been sealed by a plug member, being extruded in a similar manner at a working temperature between plasticity transition temperature and crystallization temperature of the alloy, next the core member in the extruded billet being removed by machining to thereby obtain an aimed amorphous alloy compact of cylindrical shape.
However, any detailed conditions of the compacting had not been given by the patent. Since the prior art extrusion method described above utilizes tangled loose agglomeration of filaments, there has been such a problem that it is considerably difficult to uniformly fill such tangled loose filaments into a container. Moreover, since the method has also required to perform preliminary filling in order to obtain an initial filling density of 50 to 60%, there remained such an additional problem that there was a difficulty in filling the filaments into a container of complicated shape
In addition, since the conventional extrusion technique requires at least about 70% reduction of area of the billet regarding extrusion working, considerably high extrusion load must be imparted to the billet during working, and this makes it necessary to use a large equipment.
Moreover, due to the fact that the billet must be subjected to a working of at least 70% in reduction of area, a large amount of heat occurs during the compacting working. In order to prevent the temperature rise from becoming no less than the crystallization temperature of the alloy, the temperature for the compacting had been restricted to a narrow range with the result that there was a serious problem in practical operation.